Pyrotechnic compositions and methods of making the same

ABSTRACT

Pyrotechnic compositions are provided herein. The pyrotechnic composition includes potassium nitrate (KNO 3 ), potassium perchlorate (KClO 4 ), an inorganic fuel including boron, an organic fuel including one or more of carbon, hydrogen, and oxygen, and one or more binders. The pyrotechnic composition may have one or more of: a heat of explosion (HEX) of greater than or equal to about 5.000 J/g, a maximum flame temperature at combustion (T c ) of greater than or equal to about 2,500 K (2,227° C.), and a gas yield of greater than or equal to about 15 moles/kg. Methods of preparing the pyrotechnic composition are also provided including wet granulation methods.

BACKGROUND

This section provides background information related to the present disclosure which is not necessarily prior art.

Pyrotechnic compositions including pyrotechnic materials are used in passive restraint systems, including in inflators for airbag modules. Examples of such pyrotechnic compositions include ignition booster compositions (also referred to as igniter, initiator, and/or booster compositions), as well as conventional gas generants. A gas generant material burns to produce the majority of gas products that are directed to an airbag to provide inflation. Airbag modules employing gas generants often use a squib or initiator which is electrically ignited when rapid deceleration and/or collision is sensed. The discharge from the squib/initiator can ignite an igniter or ignition material that burns rapidly and exothermically, in turn, igniting the gas generant material. Often, the initiator may include several stages that may employ one or more igniter or ignition booster compositions.

Ignition booster materials are traditionally based on pyrotechnic formulations containing combinations of titanium hydride/potassium perchlorate (THPP) or boron/potassium nitrate (BKNO3). However, when present in large amounts, compositions containing THPP can be too brisant resulting in undesirable fracturing of gas generant shapes upon deployment and/or fracturing of the hardware critical for gas generation thereby reducing reliability of a passive restraint system. On the other end of the spectrum are compositions containing BKNO3, which may produce too weak of a charge for some pyrotechnic applications, for example, resulting in unreliable inflator initiation. Consequently, it would be desirable to develop effective pyrotechnic compositions, such as ignition booster compositions, that can provide a secondary charge with an intermediate energy output capable of reliably initiating inflators or other pyrotechnic automotive safety devices with minimal to no damage to critical components of the system.

SUMMARY

This section provides a general summary of the disclosure and is not a comprehensive disclosure of its full scope or all of its features.

The present disclosure provides in certain variations a pyrotechnic composition including potassium nitrate (KNO₃), potassium perchlorate (KClO₄), an inorganic fuel comprising boron, an organic fuel comprising one or more of carbon, hydrogen, and oxygen, and one or more binders. The pyrotechnic composition may satisfy one or more of the following: (i) a heat of explosion (HEX) of greater than or equal to about 5.000 J/g; (ii) a maximum flame temperature at combustion (T_(c)) of greater than or equal to about 2.500 K (2,227° C.); and (iii) a gas yield of greater than or equal to about 15 moles/kg.

In one aspect, the potassium nitrate (KNO₃) may be present in an amount greater than or equal to about 50% to less than or equal to about 70% by weight of the pyrotechnic composition.

In one aspect, the potassium perchlorate (KClO₄) may be present in an amount greater than or equal to about 10% to less than or equal to about 30% by weight of the pyrotechnic composition.

In one aspect, the boron may be present in an amount greater than or equal to about 5% to less than or equal to about 15% by weight of the pyrotechnic composition.

In one aspect, the organic fuel may be present in an amount greater than or equal to about 3% to less than or equal to about 15% by weight of the pyrotechnic composition.

In one aspect, the organic fuel may be selected from the group consisting of: guanidine nitrate, diammonium 5,5′-bitetrazole (DABT), copper bis guanylurea dinitrate, hexamine cobalt (III) nitrate, copper diamine bitetrazole, a melamine oxalate compound, and combinations thereof.

In one aspect, the second organic fuel may include guanidine nitrate.

In one aspect, the one or more binders may be selected from the group consisting of hydroxypropyl cellulose (HPC), polyvinyl acetate, polyvinyl alcohol, polyvinyl pyrrolidone, polyacrylamide, polyacrylate, mineral oil, and a combination thereof.

In one aspect, the one or more binders may be present in an amount greater than or equal to about 0.5% to less than or equal to about 10% by weight of the pyrotechnic composition.

In one aspect, the one or more binders may include hydroxypropyl cellulose (HPC).

In one aspect, the pyrotechnic composition satisfies one or more of the following: (i) the heat of explosion (HEX) is greater than or equal to about 5,000 J/g to less than or equal to about 6,500 J/g; (ii) the maximum flame temperature at combustion (T_(c)) is greater than or equal to about 2,500 K (2,227° C.) to less than or equal to about 3,500 K (3,227° C.); and (iii) the gas yield is greater than or equal to about 15 moles/kg to less than or equal to about 30 moles/kg.

In one aspect, the one or more binders may further include mineral oil present in an amount greater than or equal to about 0.5% to less than or equal to 2% by weight of the pyrotechnic composition.

In one aspect, the pyrotechnic composition may be in a form of granules having an average particle diameter (D50) of greater than or equal to about 150 μm to less than or equal to about 850 μm.

In yet other variations, the present disclosure also provides a method of forming a pyrotechnic composition. The method includes mixing (i) potassium nitrate (KNO₃), (ii) potassium perchlorate (KClO₄), (iii) an inorganic fuel comprising boron, (iv) an organic fuel comprising one or more of carbon, hydrogen, and oxygen, (v) and one or more binders with a liquid to form a slurry. The method further includes removing at least a portion of the liquid from the slurry to form a plurality of granulated particles, sizing the plurality of granulated particles to form sized granulated particles having an average particle diameter (D50) of greater than or equal to about 150 μm to less than or equal to about 850 μm, and drying the sized granulated particles to form a solid pyrotechnic composition. The pyrotechnic composition may satisfy one or more of the following: (i) a heat of explosion (HEX) of greater than or equal to about 5,000 J/g; (ii) a maximum flame temperature at combustion (T_(c)) of greater than or equal to about 2,500 K (2,227° C.); and (iii) a gas yield of greater than or equal to about 15 moles/kg.

In one aspect, the organic fuel may be selected from the group consisting of: guanidine nitrate, diammonium 5,5′-bitetrazole (DABT), copper bis guanylurea dinitrate, hexamine cobalt (III) nitrate, copper diamine bitetrazole, a melamine oxalate compound, and combinations thereof, and the organic fuel may be present in an amount greater than or equal to about 3% to less than or equal to about 15% by weight of the pyrotechnic composition. Additionally, the one or more binders may be selected from the group consisting of hydroxypropyl cellulose (HPC), polyvinyl acetate, polyvinyl alcohol, polyvinyl pyrrolidone, polyacrylamide, polyacrylate, mineral oil, and a combination thereof, and the one or more binders may be present in an amount greater than or equal to about 0.5% to less than or equal to about 10% by weight of the pyrotechnic composition.

In one aspect, (i) the potassium nitrate (KNO₃) may be present in an amount greater than or equal to about 50% to less than or equal to about 70% by weight of the pyrotechnic composition, (ii) the potassium perchlorate (KClO₄) may be present in an amount greater than or equal to about 10% to less than or equal to about 30% by weight of the pyrotechnic composition, (iii) the boron may be present in an amount greater than or equal to about 5% to less than or equal to about 15% by weight of the pyrotechnic composition; (iv) guanidine nitrite may be present in an amount greater than or equal to about 3% to less than or equal to about 15% by weight of the pyrotechnic composition; (v) hydroxy propyl cellulose (HPC) may be present in an amount greater than or equal to about 0.5% to less than or equal to about 10% by weight of the pyrotechnic composition; and (vi) mineral oil may be present in an amount greater than or equal to about 0.5% to less than or equal to 2% by weight of the pyrotechnic composition.

Further areas of applicability will become apparent from the description provided herein. The description and specific examples in this summary are intended for purposes of illustration only and are not intended to limit the scope of the present disclosure.

DETAILED DESCRIPTION

Example embodiments are provided so that this disclosure will be thorough, and will fully convey the scope to those who are skilled in the art. Numerous specific details are set forth such as examples of specific compositions, components, devices, and methods, to provide a thorough understanding of embodiments of the present disclosure. It will be apparent to those skilled in the art that specific details need not be employed, that example embodiments may be embodied in many different forms and that neither should be construed to limit the scope of the disclosure. In some example embodiments, well-known processes, well-known device structures, and well-known technologies are not described in detail.

The terminology used herein is for the purpose of describing particular example embodiments only and is not intended to be limiting. As used herein, the singular forms “a,” “an,” and “the” may be intended to include the plural forms as well, unless the context clearly indicates otherwise. The terms “comprises,” “comprising,” “including,” and “having,” are inclusive and therefore specify the presence of stated features, elements, compositions, steps, integers, operations, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof. Although the open-ended term “comprising,” is to be understood as a non-restrictive term used to describe and claim various embodiments set forth herein, in certain aspects, the term may alternatively be understood to instead be a more limiting and restrictive term, such as “consisting of” or “consisting essentially of.” Thus, for any given embodiment reciting compositions, materials, components, elements, features, integers, operations, and/or process steps, the present disclosure also specifically includes embodiments consisting of, or consisting essentially of, such recited compositions, materials, components, elements, features, integers, operations, and/or process steps. In the case of “consisting of,” the alternative embodiment excludes any additional compositions, materials, components, elements, features, integers, operations, and/or process steps, while in the case of “consisting essentially of,” any additional compositions, materials, components, elements, features, integers, operations, and/or process steps that materially affect the basic and novel characteristics are excluded from such an embodiment, but any compositions, materials, components, elements, features, integers, operations, and/or process steps that do not materially affect the basic and novel characteristics can be included in the embodiment.

Any method steps, processes, and operations described herein are not to be construed as necessarily requiring their performance in the particular order discussed or illustrated, unless specifically identified as an order of performance. It is also to be understood that additional or alternative steps may be employed, unless otherwise indicated.

When a component, element, or layer is referred to as being “on,” “engaged to,” “connected to,” or “coupled to” another element or layer, it may be directly on, engaged, connected or coupled to the other component, element, or layer, or intervening elements or layers may be present. In contrast, when an element is referred to as being “directly on,” “directly engaged to,” “directly connected to,” or “directly coupled to” another element or layer, there may be no intervening elements or layers present. Other words used to describe the relationship between elements should be interpreted in a like fashion (e.g., “between” versus “directly between,” “adjacent” versus “directly adjacent,” etc.). As used herein, the term “and/or” includes any and all combinations of one or more of the associated listed items.

Although the terms first, second, third, etc. may be used herein to describe various steps, elements, components, regions, layers and/or sections, these steps, elements, components, regions, layers and/or sections should not be limited by these terms, unless otherwise indicated. These terms may be only used to distinguish one step, element, component, region, layer or section from another step, element, component, region, layer or section. Terms such as “first,” “second,” and other numerical terms when used herein do not imply a sequence or order unless clearly indicated by the context. Thus, a first step, element, component, region, layer or section discussed below could be termed a second step, element, component, region, layer or section without departing from the teachings of the example embodiments.

Spatially or temporally relative terms, such as “before,” “after,” “inner,” “outer,” “beneath,” “below,” “lower,” “above,” “upper,” and the like, may be used herein for ease of description to describe one element or feature's relationship to another element(s) or feature(s) as illustrated in the figures. Spatially or temporally relative terms may be intended to encompass different orientations of the device or system in use or operation in addition to the orientation depicted in the figures.

Throughout this disclosure, the numerical values represent approximate measures or limits to ranges to encompass minor deviations from the given values and embodiments having about the value mentioned as well as those having exactly the value mentioned. Other than in the working examples provided at the end of the detailed description, all numerical values of parameters (e.g., of quantities or conditions) in this specification, including the appended claims, are to be understood as being modified in all instances by the term “about” whether or not “about” actually appears before the numerical value. “About” indicates that the stated numerical value allows some slight imprecision (with some approach to exactness in the value; approximately or reasonably close to the value; nearly). If the imprecision provided by “about” is not otherwise understood in the art with this ordinary meaning, then “about” as used herein indicates at least variations that may arise from ordinary methods of measuring and using such parameters. For example, “about” may comprise a variation of less than or equal to 5%, optionally less than or equal to 4%, optionally less than or equal to 3%, optionally less than or equal to 2%, optionally less than or equal to 1%, optionally less than or equal to 0.5%, and in certain aspects, optionally less than or equal to 0.1%.

In addition, disclosure of ranges includes disclosure of all values and further divided ranges within the entire range, including endpoints and sub-ranges given for the ranges.

As used herein, the terms “composition” and “material” are used interchangeably to refer broadly to a substance containing at least the desired chemical constituents, elements, or compounds, but which may also comprise additional elements, compounds, or substances, including trace amounts of impurities, unless otherwise indicated.

As used herein, unless otherwise indicated, amounts expressed in weight and mass are used interchangeably, but should be understood to reflect a mass of a given component.

The present disclosure provides a pyrotechnic composition, which may also be referred to as an igniter composition, an initiator composition, or a booster composition. In certain variations, such a pyrotechnic composition provides one or more of the following advantages: slower burning yet sufficient heat output, intermediate energy output, ease of ignition, high combustion flame temperatures, efficient combustion at low pressures, and/or effective transfer of energy to an acceptor composition, for example, the main gas generant material, as will be described further below. It is understood that while general attributes of each of the above categories of components may differ, there may be some common attributes and any given material may serve multiple purposes within two or more of such listed classes or categories. For example, guanidine nitrate may serve as an organic fuel as well as a binder in the pyrotechnic composition.

In various aspects, the pyrotechnic compositions provided in accordance with the present disclosure may serve as effective ignition booster compositions, which are relatively safe to handle and produce for use in automotive and other pyrotechnic devices. Such pyrotechnic compositions can be handled and processed in a manner more similar to those of conventional gas generants.

The pyrotechnic composition may include a combination of one or more oxidizers, one or more fuels, and one or more binders. In certain variations, the pyrotechnic composition comprises a combination of multiple oxidizers, for example, such that the oxidizers may be nominally considered a primary oxidizer, a second oxidizer, and the like. One or more oxidizers are selected along with a hot burning inorganic fuel component to form an igniter material that upon combustion achieves an effectively high burn rate and energy transfer to a gas generant material.

Suitable oxidizers for the pyrotechnic composition of the present disclosure generally include, by way of non-limiting example, alkali metal (e.g., elements of Group 1 of IUPAC Periodic Table, including Li, Na, K, Rb, and/or Cs), alkaline earth metal (e.g., elements of Group 2 of IUPAC Periodic Table, including Be, Ng, Ca, Sr, and/or Ba), and ammonium nitrates, nitrites, and perchlorates; metal oxides (including Cu, Mo, Fe, Bi, La, and the like); basic metal nitrates (e.g., elements of transition metals of Row 4 of IUPAC Periodic Table, including Mn, Fe, Co, Cu, and/or Zn); transition metal complexes of ammonium nitrate (e.g., elements selected from Groups 3-12 of the IUPAC Periodic Table); metal ammine nitrates, metal hydroxides, and combinations thereof.

In certain variations, an oxidizer in the pyrotechnic composition may be selected from the group consisting of: alkali metal, alkaline earth metal, and nitrates and perchlorates. For example, one or more oxidizers may include potassium nitrate (KNO_(3′) also referred to nominally as KP), potassium perchlorate (KClO₄), or a combination of a potassium nitrate (KNO₃) and potassium perchlorate (KClO₄). In certain variations, the oxidizers may include potassium nitrate (KNO₃) and potassium perchlorate (KClO₄). In such an embodiment, this combination of oxidizers may provide for good reactivity based on inclusion of the potassium perchlorate and advantageous reduction in handling sensitivity to moisture due to the presence of the nitrate-containing oxidizer. In certain aspects, potassium nitrate is employed as the nitrate oxidizer, because it has low moisture sensitivity and does not impart moisture sensitivity to the final igniter composition.

Individual oxidizing agents may be respectively present in a pyrotechnic composition in an amount, by weight of the pyrotechnic composition, of greater than or equal to about 5%, greater than or equal to about 10%, greater than or equal to about 20%, greater than or equal to about 30%, greater than or equal to about 40%, greater than or equal to about 50%, greater than or equal to about 60%, greater than or equal to about 70%, or about 75%; or from greater than or equal to about 5% to less than or equal to about 75% by weight, greater than or equal to about 10% to less than or equal to about 70% by weight, greater than or equal to about 20% to less than or equal to about 70% by weight, greater than or equal to about 40% to less than or equal to about 70% by weight, greater than or equal to about 50% to less than or equal to about 70% by weight, greater than or equal to about 5% to less than or equal to about 40% by weight, or greater than or equal to about 10% to less than or equal to about 30% by weight. In any embodiment, the cumulative total amount of all oxidizer(s) in the pyrotechnic composition, by weight of the pyrotechnic composition, may be greater than or equal to about 60% to less than or equal to about 95% by weight, optionally greater than or equal to about 70% to less than or equal to about 90% by weight, or optionally greater than or equal to about 80% to less than or equal to about 90% by weight. Additionally or alternatively, an oxidizer, such as potassium nitrate (KNO₃), may be present in the pyrotechnic composition in an amount, based on weight of the pyrotechnic composition, of greater than or equal to about 50% to less than or equal to about 70% by weight or greater than or equal to about 60% to less than or equal to about 70% by weight. In addition to potassium nitrate (KNO₃), a further oxidizer, such as potassium perchlorate (KClO₄), may be present in the pyrotechnic composition in an amount, based on weight of the pyrotechnic composition, of greater than or equal to about 10% to less than or equal to about 30% by weight or greater than or equal to about 20% to less than or equal to about 30% by weight.

In any embodiment, the pyrotechnic composition may include a first fuel and a second fuel. The first fuel may be an inorganic fuel that is a hot burning fuel, such as boron. It is contemplated herein that the term “boron” includes elemental boron as well as boron-containing compounds. The first fuel or inorganic fuel (e.g., boron) may be present in the pyrotechnic composition in an amount, based on weight of the pyrotechnic composition, of greater than or equal to about 2.5%, greater than or equal to about 5%, greater than or equal to about 10%, less than or equal to about 20%, or less than or equal to 15%; or from greater than or equal to about 2.5% to less than or equal to about 20% by weight, greater than or equal to about 5% to less than or equal to about 15% by weight, greater than or equal to about 10% to less than or equal to about 15% by weight. It is also contemplated herein that the first fuel may further include an additional inorganic fuel. The additional inorganic fuel may include an elemental metal (e.g., titanium (Ti), silicon (Si), aluminum (Al), magnesium (Mg), iron (Fe), and combinations thereof) or metal hydride (e.g., titanium hydride (TiH₂)).

The second fuel may be any suitable organic fuel containing one or more of carbon, hydrogen, oxygen, and nitrogen that produces gas, such CO₂, N₂, and/or H₂O, upon combustion to pressurize a combustion chamber, which improves ignitability of the igniter and gas generant via pressurization as well as dissemination of hot particulate into the pyrotechnic charges being lit. Examples of suitable organic fuels include, but are not limited to, guanidine nitrate, diammonium 5,5′-bitetrazole (DABT), copper bis guanylurea dinitrate, hexamine cobalt (III) nitrate, copper diamine bitetrazole, a melamine oxalate compound, or combinations thereof. In various aspects, the organic fuel may be guanidine nitrate. The organic fuel may be present in the pyrotechnic composition, based on weight of the pyrotechnic composition, in an amount of greater than or equal to about 1%, greater than or equal to about 3%, greater than or equal to about 5%, less than or equal to about 20%, less than or equal to about 15%, or less than or equal to about 10%; or from greater than or equal to about 1% to less or equal to about 20% by weight, greater than or equal to about 3% to less than or equal to about 15% by weight, or greater than or equal to about 5% to less than or equal to about 15% by weight.

In various aspects, the igniter compositions according to certain aspects of the present disclosure also includes one or more binders, such as polymeric binders. Binders are commonly used in pyrotechnic compositions to increase adhesion/bonding to retain the shape of the various pyrotechnic solid components, particularly when they are formed via extrusion and/or molding, and to prevent fracture during storage and use. Typically, pyrotechnic compositions are not capable of being tableted or formed into pellets due to the sensitivity of the raw materials. However, as described further below, the present disclosure contemplates methods of making igniter compositions that may be in the form of tablets, pellets, or grains and thus include binders appropriate for a pyrotechnic composition (for example, having a high burn rate to maintain effective ballistic properties for an igniter). Binders used in a pyrotechnic composition may have some fuel value (and may be considered to be a fuel in a conventional gas generant) and thus may be considered to be a co-fuel, but such binders generally do not have a high enough burn rate to serve as a primary fuel in a pyrotechnic composition that requires a high burn rate and rapid reaction. Thus, in certain variations, a dry blended mixture of various pyrotechnic components can be mixed with a liquid binder and form granules as further described below. Alternatively, solid binder particles can be dissolved in a solvent or heated to the melting point, then mixed with other pyrotechnic components and form granules as further described below. In accordance with certain variations of the present disclosure, binders may contribute to the igniter composition as a slower burning fuel. Suitable binders in accordance with the present disclosure may include, but are not limited to, hydroxypropyl cellulose (HPC), polyvinyl acetate, polyvinyl alcohol, polyvinyl pyrrolidone, polyacrylamide, polyacrylate, mineral oil, or combinations thereof. The term “mineral oil” refers to a clear colorless nearly odorless and tasteless liquid obtained from the distillation of petroleum including a mixture of higher alkanes (e.g., C₉ or higher alkanes). It may also be referred to as white oil, white mineral oil, liquid petrolatum, liquid paraffin, or white paraffin oil. For example, a pyrotechnic composition in accordance with the present disclosure may include a polymeric binder, such as hydroxypropyl cellulose (HPC), and optionally an additional binder, such as mineral oil.

Binders may be present in a pyrotechnic composition according to certain aspects of the present disclosure in an amount, based on weight of the pyrotechnic composition, of greater than or equal to about 0.5%, greater than or equal to about 1%, greater than or equal to about 2.5%, less than or equal to about 10%, less than or equal to about 7.5%, or less than or equal to about 5%; or from greater than or equal to about 0.5% to less than or equal to 10% by weight, greater than or equal to 1% to less than or equal to about 7.5%, or greater than or equal to about 1% to less than or equal to about 5% by weight. For example, a pyrotechnic composition in accordance with the present disclosure may include a polymeric binder, such as hydroxypropyl cellulose (HPC) in an amount, based on weight of the pyrotechnic binder, of greater than or equal to about 0.5% to less than or equal to about 10% by weight or greater than or equal to about 1% to less than or equal to about 5% by weight, and optionally an additional binder, such as mineral oil, in an amount, based on weight of the pyrotechnic composition, of greater than or equal to about 0.5% by weight, greater than or equal to about 1% by weight, or less than or equal to about 2% by weight (e.g., greater than or equal to 0.5% to less than or equal to about 2% by weight or greater than or equal to about 1% to less than or equal to about 2% by weight). In some embodiment, mineral oil may not be substantially present (e.g., less than or equal 0.1% by weight or 0 (zero) % by weight) in the pyrotechnic composition.

In certain variations of the present disclosure, the pyrotechnic composition includes (i) potassium nitrate (KNO₃) in an amount greater than or equal to about 50% by weight of the pyrotechnic composition, for example, greater than or equal to about 50% to less than or equal to about 70% by weight; (ii) potassium perchlorate (KClO₄) in an amount greater than or equal to about 10% by weight of the pyrotechnic composition, for example, greater than or equal to about 10% to less than or equal to about 30% by weight; (iii) an inorganic fuel comprising boron in an amount greater than or equal to about 5% by weight of the pyrotechnic composition, for example, greater than or equal to about 5% to less than or equal to about 15% by weight; (iv) an organic fuel selected from the group consisting of: guanidine nitrate, diammonium 5,5′-bitetrazole (DABT), copper bis guanylurea dinitrate, hexamine cobalt (III) nitrate, copper diamine bitetrazole, a melamine oxalate compound, and combinations thereof, in an amount greater than or equal to about 3% by weight of the pyrotechnic composition, for example, greater than or equal to about 3% to less than or equal to about 15% by weight; and (v) one or more binders selected from the group consisting of: hydroxypropyl cellulose (HPC), polyvinyl acetate, polyvinyl alcohol, polyvinyl pyrrolidone, polyacrylamide, polyacrylate, mineral oil, and a combination thereof, in an amount greater than or equal to about 0.5% by weight of the pyrotechnic composition, for example, greater than or equal to about 0.5% to less than or equal to about 10% by weight.

In certain variations of the present disclosure, the pyrotechnic composition includes (i) potassium nitrate (KNO₃) in an amount greater than or equal to about 50% by weight of the pyrotechnic composition, for example, greater than or equal to about 50% to less than or equal to about 70% by weight; (ii) potassium perchlorate (KClO₄) in an amount greater than or equal to about 10% by weight of the pyrotechnic composition, for example, greater than or equal to about 10% to less than or equal to about 30% by weight; (iii) an inorganic fuel comprising boron in an amount greater than or equal to about 5% by weight of the pyrotechnic composition, for example, greater than or equal to about 5% to less than or equal to about 15% by weight; (iv) an organic fuel comprising guanidine nitrate in an amount greater than or equal to about 3% by weight of the pyrotechnic composition, for example, greater than or equal to about 3% to less than or equal to about 15% by weight; (v) hydroxypropyl cellulose (HPC) in an amount greater than or equal to about 0.5% by weight of the pyrotechnic composition, for example, greater than or equal to about 0.5% to less than or equal to about 10% by weight; and (vi) mineral oil in an amount an amount of greater than or equal to 0.5% by weight of the pyrotechnic composition, for example, greater than or equal to about 0.5% to less than or equal to about 2% by weight.

In various aspects, the combination of above-described oxidizers (e.g., potassium nitrate (KNO₃), potassium perchlorate (KClO₄)), inorganic fuel (e.g., boron), organic fuel (e.g., guanidine nitrate), and binders (e.g., hydroxypropyl cellulose (HPC), mineral oil) in the pyrotechnic composition advantageously results in a less brisant combustion that can still provide sufficient gas production and energy output for reliable initiation of inflators. Brisance is generally understood to be the propensity of a given material to react in mass or an expression of the violence of the reaction. The reduction in brisance in the pyrotechnic compositions provided by the present disclosure helps reduce damage to the acceptor gas generant charge along with the sufficient gas production helps pressurize the inflator combustion chamber resulting in in enhanced ignition performance. A combination of properties including heat of explosion, flame temperature, and/or gas yield for pyrotechnic compositions according to the present disclosure contributes to this desirable reduction in brisance along with sufficient gas production.

For example, a pyrotechnic composition as described herein may have a heat of explosion (HEX) of greater than or equal to about 3,000 J/g, greater than or equal to about 4,000 J/g, greater than or equal to about 5,000 J/g, less than or equal to about 8,000 J/g, less than or equal to about 7,000 J/g, less than or equal to about 6,500 J/g, or less than or equal to about 6,000 J/g; or from greater than or equal to about 3,000 J/g to less than or equal to about 8,000 J/g, greater than or equal to about 4,000 J/g to less than or equal to about 7,000 J/g, greater than or equal to about 5,000 J/g to less than or equal to about 6,500 J/g, or greater than or equal to about 5,000 J/g to less than or equal to about 6,000 J/g.

Additionally or alternatively, a pyrotechnic composition as described herein may have a maximum flame temperature at combustion (T_(c)) of greater than or equal to about 1500 K (1,227° C.), greater than or equal to about 2,000 K (1,727° C.), greater than or equal to about 2,500 K (2,227° C.), greater than or equal to about 3,000 K (2,727° C.), less than or equal to about 4,500 K (4,227° C.), less than or equal to about 4,000 K (3,727° C.), less than or equal to about 3,500 K (3,227° C.); or from greater than or equal to about 1,500 K (1,227° C.) to less than or equal to 4,500 K (4,227° C.), greater than or equal to about 2,000 K (1,727° C.) to less than or equal to 4,000 K (3,727° C.) greater than or equal to about 2,500 K (2,227° C.) to less than or equal to 3,500 K (3,227° C.), or greater than or equal to about 3000 K (2,727° C.) to less than or equal to 3,500 K (3,227° C.).

Additionally or alternatively, pyrotechnic composition as described herein may have a gas yield of greater than or equal to about 7.5 moles/kg, greater than or equal to about 10 moles/kg greater than or equal to about 15 moles/kg, greater than or equal to about 20 moles/kg, less than or equal to about 40 moles/kg, less than or equal to about 35 moles/kg, less than or equal to about 30 moles/kg, or less than or equal to about 25 moles/kg; or from greater than or equal to about 7.5 moles/kg to less than or equal to about 40 moles/kg, greater than or equal to about 10 moles/kg to less than or equal to about 35 moles/kg, greater than or equal to about 15 moles/kg to less than or equal to about 30 moles/kg, or greater than or equal to about 15 moles/kg to less than or equal to about 25 moles/kg.

In various aspects, pyrotechnic composition as described herein may have one or more, two or more, or all of the following properties: (i) a heat of explosion (HEX) of greater than or equal to about 5,000 J/g, for example, greater than or equal to about 5,000 J/g to less than or equal to about 6,500 J/g; (ii) a maximum flame temperature at combustion (T_(c)) of greater than or equal to about, 2500 K (2,227° C.), for example, greater than or equal to about 2,500 K (2,227° C.) to less than or equal to about 3,500 K (3,227° C.); (iii) a gas yield of greater than or equal to about 15 moles/kg, for example, greater than or equal to about 15 moles/kg to less than or equal to about 30 moles/kg.

The pyrotechnic composition may also include other suitable pyrotechnic additives known to those of skill in the art in minor amounts, such as pressing aids, anti-caking agents, slagging agents, dispersing aids, flow aids, viscosity modifiers, phlegmatizing agents, and the like. Generally, such pyrotechnic additives may be respectively included in the igniter composition in an amount of greater than zero (0) to less than or equal to about 5 weight %.

In any embodiment, the pyrotechnic compositions of the present disclosure may advantageously be in formed into granules or particles via wet granulation techniques further described below. In such instances, extrusion and molding process are not needed to form the pyrotechnic compositions provided herein. For example, the pyrotechnic composition may have an average particle diameter (D50) of greater than or equal to about 50 μm, greater than or equal to about 100 μm, greater than or equal to about 150 μm, greater than or equal to about 250 μm, greater than or equal to about 300 μm, greater than or equal to about 400 μm, greater than or equal to about 500 μm, less than or equal to about 1000 μm, less than or equal to about 900 μm, less than or equal to about 850 μm, less than or equal to about 800 μm, less than or equal to about 700 μm, less than or equal to about 600 μm; or from greater than or equal to about 50 μm to less than or equal to about 1000 μm, greater than or equal to about 100 μm to less than or equal to about 900 μm, greater than or equal to about 150 μm to less than or equal to about 850 μm, or greater than or equal to about 200 μm to less than or equal to about 800 μm. In any embodiment, pyrotechnic compositions of the present disclosure may have an average particle diameter (D50) of greater than or equal to about 150 μm to less than or equal to about 850 μm.

In various aspects, methods of forming pyrotechnic compositions according to the present disclosure are provided herein. The method may be a wet granulation method to form a solid pyrotechnic composition in granule form having an average particle diameter (D50) as described above. In any embodiment, the method may include mixing one or more oxidizers as described herein (e.g., potassium nitrate (KNO₃), potassium perchlorate (KClO₄), an inorganic fuel as described herein (e.g., boron), an organic fuel as described herein (e.g., guanidine nitrate, diammonium 5,5′-bitetrazole (DABT), copper bis guanylurea dinitrate, hexamine cobalt (III) nitrate, copper diamine bitetrazole, a melamine oxalate compound), and one or more binders as described herein (e.g., hydroxypropyl cellulose (HPC), polyvinyl acetate, polyvinyl alcohol, polyvinyl pyrrolidone, polyacrylamide, polyacrylate, mineral oil) with a liquid to form a slurry. For example, in the mixture, (i) potassium nitrate (KNO₃) may be present in an amount greater than or equal to about 50% by weight of the pyrotechnic composition, for example, greater than or equal to about 50% to less than or equal to about 70% by weight of the pyrotechnic composition; (ii) potassium perchlorate (KClO₄) may be present in an amount greater than or equal to about 10% by weight of the pyrotechnic composition, for example, greater than or equal to 10% to less than or equal to about 30% by weight of the pyrotechnic composition; (iii) boron may be present in an amount greater than or equal to about 5% by weight of the pyrotechnic composition, for example, greater than or equal to about 5% to less than or equal to about 15% by weight of the pyrotechnic composition; (iv) organic fuel, such as guanidine nitrate, may be present in an amount greater than or equal to about 3% by weight of the pyrotechnic compositions, for example, greater than or equal to about 3% to less than or equal to about 15% by weight of the pyrotechnic composition; (v) one or more binders, such as hydroxy propyl cellulose (HPC), may be present in an amount greater than or equal to about 0.5% by weight of the pyrotechnic composition, for example, greater than or equal to about 0.5% to less than or equal to about 10% by weight of the pyrotechnic composition; and (vi) mineral oil optionally may be present in an amount greater than or equal to about 0.5% by weight of the pyrotechnic composition, for example, greater than or equal to about 0.5% to less than or equal to 2% by weight of the pyrotechnic composition.

It is contemplated herein that the one or more oxidizers, inorganic fuel, organic fuel, and one or more binders may be in dry form, such as a powder, and dry blended together prior to mixing with a liquid to form the slurry. The liquid may be any suitable carrier. Suitable carriers include aqueous solutions that may be mostly water; however, the carrier may also contain one or more organic solvents or alcohols. In some embodiments, the carrier may include an azeotrope, which refers to a mixture of two or more liquids, such as water and certain alcohols that desirably evaporate in constant stoichiometric proportion at specific temperatures and pressures. The carrier is selected for compatibility with the fuel and oxidizer components to avoid adverse reactions and further to maximize solubility of the several components forming the slurry. Non-limiting examples of suitable carriers include water, isopropyl alcohol, n-propyl alcohol, ethanol and combinations thereof. In some embodiments, the slurry has a liquid content, based on weight of the slurry, of greater than or equal to about 5% by weight, greater than or equal to about 10% by weight, optionally about 15% by weight, or optionally about 20% by weight. In some embodiments, a liquid content of the slurry ranges from about 10% to 15% by weight of the slurry. In some embodiments, the slurry has a viscosity ranging from about 50,000 to 250,000 centipoise. Such viscosities are believed to be desirable to provide suitable rheological properties that allow the slurry to flow under applied pressure, but also permit the slurry to remain stable.

After forming the slurry, at least a portion of the liquid may be removed from the slurry to form a plurality of granulated particles. For example, a liquid content from the slurry may be reduced by greater than or equal to about 1% by weight, greater than or equal to about 2% by weight, greater than or equal to about 3% by weight, or about 5% by weight. For example, if the slurry has a liquid content of about 15% by weight, following removal of a portion of the liquid, the plurality of granulated particles may have liquid content that is 2% by weight less than the liquid content of the slurry, i.e., the plurality of granulated particles have a liquid content of 13% by weight. Removal of the liquid can be performed by any suitable method including introduction of air into a vessel mixing the slurry.

The plurality of granulated particles may undergo a sizing step to form sized granulated particles having an average particle diameter (D50) as described herein, for example, greater than or equal to about 150 μm to less than or equal to about 850 μm or greater than or equal to about 200 μm to less than or equal to about 800 μm. The sizing step may be performed with any suitable equipment for sizing granulated particles. For example, screens having openings with appropriate diameters may be used, and the plurality of granulated particles may be pushed through the screens to form the sized granulated particles. Once sized, the sized granulated particles may undergo further drying to form a solid pyrotechnic composition as described herein. If necessary, the solid pyrotechnic composition optionally may undergo further sizing.

In various aspects, the solid pyrotechnic composition may have one or more, two or more, or all of the following properties: (i) a heat of explosion (HEX) of greater than or equal to about 5,000 J/g, for example, greater than or equal to about 5,000 J/g to less than or equal to about 6,500 J/g; (ii) a maximum flame temperature at combustion (T_(c)) of greater than or equal to about 2,500 K (2,227° C.), for example, greater than or equal to about 2,500 K (2,227° C.) to less than or equal to about 3,500 K (3,227° C.); (iii) a gas yield of greater than or equal to about 15 moles/kg, for example, greater than or equal to about 15 moles/kg to less than or equal to about 30 moles/kg. As noted above, the pyrotechnic composition prepared in accordance with various aspects of the present disclosure may have advantageous safety properties including a reduced brisance.

Various embodiments of the inventive technology can be further understood by the specific examples contained herein. Specific Examples are provided for illustrative purposes of how to make and use the compositions, devices, and methods according to the present teachings.

Examples 1-4

The below Examples 1-4 in Table 1 were produced by first weighing each of the constituents listed in Table 1 according to the listed % by weight. The ingredients where then added to a mixing vessel and blended for approximately three minutes to provide a homogeneous mixture of the ingredients. The blending time can be greater or lesser than three minutes, but should be of a sufficient amount of time to ensure that a homogeneous mixture is produced.

After blending the ingredients, a first granulation step is conducted where at least one processing liquid is added to the mixture of dry ingredients at a controlled flow rate. As the processing liquid(s) are added, the mixture of ingredients will begin to form granules. The rate at which the processing liquid(s) are added to the mixture, as well as the amount of the processing liquid(s) that are added to the mixture, may assist in controlling the formation of the granules. After conducting the first granulation step where the granules begin to form, the mixture is subjected to a second granulation step where initial granule sizing takes place in the mixing vessel. In this regard, during the second granulation step, a temperature and pressure of the air surrounding the mixing vessel, mixing speed, mixing time, and temperature of the mixture may be monitored and controlled. For safety purposes, it should be understood that the total amount (i.e., mass) of the mixture that can be added to the mixing vessel may be controlled and/or limited by a capacity of the mixing vessel and a size of a vent of the mixing vessel.

After conducting the second granulation step, the wet granules may be removed from the mixing vessel and subjected to a first sizing process. Sizing of the granules may include passing the wet granules through a plurality of screens having openings having pre-selected and different sizes to collect granules having the desired size (e.g., an average particle diameter (D50) greater than or equal to 50 μm and less than or equal to 1000 μm). Sizing processes that use equipment other than the above-noted screens are contemplated, and the present disclosure should not be limited to the use of screens.

After the first sizing process, the collected granules may be subjected to a weathering process. Weathering of the collected granules may include at least partially drying the collected granules. Other weathering processes known to those skilled in the art may also be used, without limitation. The weathered granules may then be subjected to a second sizing process to obtain a granules having a specific size. The second sizing process may be similar to the first sizing process, but use different screens or equipment to obtain the desired average particle diameter (D50) for the granules (e.g., greater than or equal to 200 μm and less than or equal to 800 μm).

Regardless of whether a second sizing process is conducted, the weathered granules may then be subjected to a drying process to remove the processing liquid(s) to the desired extent. The method for drying the granules may include using a blower to dry the granules, or subjecting the granules to a temperature for an amount of time that is sufficient to dry the granules. After drying, the granules may then be subjected to a classification step where a plurality of granules having different average particle diameters (D50) are collected in a desired distribution. For example, some of the granules may have a large average particle diameter (D50) and some of the granules may have a smaller average particle diameter (D50). The distribution of the amounts of each average particle size can be varied and tailored to meet any specific requirement.

TABLE 1 Example 1 Example 2 Example 3 Example 4 % KNO3 59.86 57.00 62.00 54.44 % KClO4 21.00 25.00 17.00 21.00 % Guanidine 7.04 4.50 10.00 12.46 Nitrate % B 10.20 12.00 8.00 10.20 % Mineral oil 1.25 1.00 1.50 1.25 % HPC 0.65 0.50 1.50 0.65 Tf K 3072 3349 2763 3195 Gn mole/kg 19.42 18.34 20.86 20.75 HEX J/g 5500 5799 5300 5969

The above-noted examples each include oxidizers (e.g., KNO₃ and KClO₄), fuels (e.g., guanidine nitrate and boron), and binders (e.g., HPC and mineral oil). While not included in the above-noted example compositions, it should be understood that the compositions may include, to some extent, additional ingredients such as processing aids that are not fully removed during granule formation.

The foregoing description of the embodiments has been provided for purposes of illustration and description. It is not intended to be exhaustive or to limit the disclosure. Individual elements or features of a particular embodiment are generally not limited to that particular embodiment, but, where applicable, are interchangeable and can be used in a selected embodiment, even if not specifically shown or described. The same may also be varied in many ways. Such variations are not to be regarded as a departure from the disclosure, and all such modifications are intended to be included within the scope of the disclosure. 

What is claimed is:
 1. A pyrotechnic composition comprising: potassium nitrate (KNO₃); potassium perchlorate (KClO₄); an inorganic fuel comprising boron; an organic fuel comprising one or more of carbon, hydrogen, and oxygen; and one or more binders; wherein the composition satisfies one or more of the following: (i) a heat of explosion (HEX) of greater than or equal to about 5,000 J/g; (ii) a maximum flame temperature at combustion (T_(c)) of greater than or equal to about 2,500 K (2,227° C.); and (iii) a gas yield of greater than or equal to about 15 moles/kg.
 2. The pyrotechnic composition of claim 1, wherein the potassium nitrate (KNO₃) is present in an amount greater than or equal to about 50% to less than or equal to about 70% by weight of the pyrotechnic composition.
 3. The pyrotechnic composition of claim 1, wherein the potassium perchlorate (KClO₄) is present in an amount greater than or equal to about 10% to less than or equal to about 30% by weight of the pyrotechnic composition.
 4. The pyrotechnic composition of claim 1, wherein the boron is present in an amount greater than or equal to about 5% to less than or equal to about 15% by weight of the pyrotechnic composition.
 5. The pyrotechnic composition of claim 1, wherein the organic fuel is present in an amount greater than or equal to about 3% to less than or equal to about 15% by weight of the pyrotechnic composition.
 6. The pyrotechnic composition of claim 1, wherein the organic fuel is selected from the group consisting of: guanidine nitrate, diammonium 5,5′-bitetrazole (DABT), copper bis guanylurea dinitrate, hexamine cobalt (III) nitrate, copper diamine bitetrazole, a melamine oxalate compound, and combinations thereof.
 7. The pyrotechnic composition of claim 1, wherein the second organic fuel comprises guanidine nitrate.
 8. The pyrotechnic composition of claim 1, wherein the one or more binders are selected from the group consisting of hydroxypropyl cellulose (HPC), polyvinyl acetate, polyvinyl alcohol, polyvinyl pyrrolidone, polyacrylamide, polyacrylate, mineral oil, and a combination thereof.
 9. The pyrotechnic composition of claim 1, wherein the one or more binders are present in an amount greater than or equal to about 0.5% to less than or equal to about 10% by weight of the pyrotechnic composition.
 10. The pyrotechnic composition of claim 1, wherein the one or more binders comprise hydroxypropyl cellulose (HPC).
 11. The pyrotechnic composition of claim, wherein the composition satisfies one or more of the following: (i) the heat of explosion (HEX) is greater than or equal to about 5,000 J/g to less than or equal to about 6,500 J/g; (ii) the maximum flame temperature at combustion (T_(c)) is greater than or equal to about 2,500 K (2,227° C.) to less than or equal to about 3,500 K (3,227° C.); and (iii) the gas yield is greater than or equal to about 15 moles/kg to less than or equal to about 30 moles/kg.
 12. The pyrotechnic composition of claim 10, wherein the one or more binders further comprise mineral oil present in an amount greater than or equal to about 0.5% to less than or equal to 2% by weight of the pyrotechnic composition.
 13. The pyrotechnic composition of claim 1, wherein the composition is in a form of granules having an average particle diameter (D50) of greater than or equal to about 150 μm to less than or equal to about 850 μm.
 14. A method for forming a pyrotechnic composition comprising: mixing (i) potassium nitrate (KNO₃), (ii) potassium perchlorate (KClO₄), (iii) an inorganic fuel comprising boron, (iv) an organic fuel comprising one or more of carbon, hydrogen, and oxygen, (v) and one or more binders with a liquid to form a slurry; removing at least a portion of the liquid from the slurry to form a plurality of granulated particles; sizing the plurality of granulated particles to form sized granulated particles having an average particle diameter (D50) of greater than or equal to about 150 μm to less than or equal to about 850 μm; and drying the sized granulated particles to form a solid pyrotechnic composition, wherein the composition satisfies one or more of the following: (i) a heat of explosion (HEX) of greater than or equal to about 5,000 J/g; (ii) a maximum flame temperature at combustion (Tc) of greater than or equal to about 2,500 K (2,227° C.); and (iii) a gas yield of greater than or equal to about 15 moles/kg.
 15. The method of claim 14, wherein: (i) the organic fuel is selected from the group consisting of: guanidine nitrate, diammonium 5,5′-bitetrazole (DABT), copper bis guanylurea dinitrate, hexamine cobalt (III) nitrate, copper diamine bitetrazole, a melamine oxalate compound, and combinations thereof and the organic fuel is present in an amount greater than or equal to about 3% to less than or equal to about 15% by weight of the pyrotechnic composition; and (ii) the one or more binders are selected from the group consisting of hydroxypropyl cellulose (HPC), polyvinyl acetate, polyvinyl alcohol, polyvinyl pyrrolidone, polyacrylamide, polyacrylate, mineral oil, and a combination thereof and the one or more binders are present in an amount greater than or equal to about 0.5% to less than or equal to about 10% by weight of the pyrotechnic composition.
 16. The method of claim 15, wherein: (i) the potassium nitrate (KNO₃) is present in an amount greater than or equal to about 50% to less than or equal to about 70% by weight of the pyrotechnic composition; (ii) the potassium perchlorate (KClO₄) is present in an amount greater than or equal to about 10% to less than or equal to about 30% by weight of the pyrotechnic composition; (iii) the boron is present in an amount greater than or equal to about 5% to less than or equal to about 15% by weight of the pyrotechnic composition; (iv) guanidine nitrite is present in an amount greater than or equal to about 3% to less than or equal to about 15% by weight of the pyrotechnic composition; (v) hydroxy propyl cellulose (HPC) is present in an amount greater than or equal to about 0.5% to less than or equal to about 10% by weight of the pyrotechnic composition; and (vi) mineral oil is present in an amount greater than or equal to about 0.5% to less than or equal to 2% by weight of the pyrotechnic composition. 